US Navy Magnetic Loop Receiving Stations

The following locations had Loop Stations established

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Magnetic Loop Detection Supplementing the various electronic detection systems, two underwater magnetic detection cables, totaling 90,185 feet of submarine cable, were laid on the bay floor just south of Beavertail Point and extending across the enytrances of East and West Passages of Narragansett Bay. The system terminated into the basement of the HECP. The loops conveniently were oriented east to west, opposite to the earth's terrestrial magnetic field and allowed sensitive calibration. When a steel-hulled vessel crossed over the loops and distorted the calibrated field, sensitive galvanometers and flux meters registered minute levels of electrical distortion induced into the cable. The cables came ashore northwest of the US Coast Guard Lighthouse and terminated in an un-occupied building north of the lighthouse.The signals were amplified and relayed to the HECP for the indicator devices. Raised concrete pedestals in the lower level of the HECP were used to provide solid non-vibration bases for the undewater detection instrumentation. Direction and speed could be calculated when a vessel crossed two points of the loop array. Tracking accuracy's are not known. The detection loops were removed by the Navy 16 July 1944, although the war with Germany was still in progress and submarines were still in the Atlantic.